We have discovered some intermittent publishing and preflight errors in layouts that is estimated to impact 1% of the currently existing layouts. (Specifically older layouts that use multiple card mapping rules with the same title).
The problem manifests itself by not showing any updates in the preflight app, or not propagating updates on affected layouts on a production app.
Engineers are investigating a permanent fix, however there is already an available work-around.
If you encounter this issue, these are the steps to mitigate it:
edit the all layouts that have mapping rules with identical titles (a simple 1dip margin change will do) and save the changes
invoke preflight for your project
publish the those layouts
This will fix the issue and your project will be fully operational.
I will provide updates as soon as the issue is permanently fixed.